Compressor



June 6, 1939. GUSTAFSQN 2,160,860

COMPRESSOR Filed .Feb. 20, 1956 4 Sheets-Sheet l I GilfZ O/(FOIY 4444 1X TO/F'A EVS.

June 6, 1939. A. N GUSTAFSON 2,150,860v

COMPRESSOR Filed Feb. 20, 1936 4 Sheets-Sheet 2 Wrawroe Arra 446/5,

u 1939; A. N. GUSVTAFSON 2,150,860 I COMPRESSOR Filed Feb. 20, 1936 4Sheets-Sheet 5 F/GJ.

W/ T/VESS:

June 6. 1939. A. N GUSTAFSON 2,160,860

COMPRESSOR Filed Feb. 20, 1956 4 Sheets-Sheet 4 Patented June 6, 1939UNITED STATES COMPRESSOR Alfred N. Gustafson, West Chester, Pa.,assignor to Schramm,

Incorporated, a corporation of Pennsylvania.

West Chester, Pa.,

Application February 20, 1936, Serial No. 64,808 I 4 Claims.

This invention relates to a compressor and more particularly to is,particularly effective in increasing the ciliciency of a compressor andreducing its size for 5 a given capacity. I

While certain aspects of the present invention are of generalapplicability to compressors of a reciprocating piston type, theinvention is particularly directed to the type of compressor which maybe regarded as constructed by a conversion of. an internal combustionengine. The transformation of internal combustion engines ,intocompressors constitutes a very economical method of producing high speedcompressors.

.The engines are quite inexpensive because of quantity production andtheir running parts are 'so made as to be capable of operation at veryhigh speeds. When'large size compressorsare produced by suchtransformation, all the cylin-v ao ders of a multi-cylinder engine maybe turned into compressor cylinders. On the other hand, where smallcompressor units are to be provided only some of the cylinders may betransformed, the remaining ones being left to function as enginecylinders so that a combination engine and compressor is provided. Asatisfactory arrangement of this latter sort is illustrated in SchrammPatent No. 1,738,121, dated December 3, 1929. As shown in this patent,the two end 30 cylinders of a four-cylinder engine have been transformedinto compressor cylinders, while the two intermediate cylinders continueto function as engine cylinders. In cases where all of the :cylindersare transformed, there is, of course,

35 used'a separate motor or engine for driving purposes.

In accordance with the practice heretofore used, there has beensubstituted a modified cylinder head in order that a greater compressionra- 40 tio may be attained in the compression cylinders than would bepermissible in engine cylinders, this substitution of head being alsoaccomplished by elimination of the mechanically operated engine valvesassociated with the compressor cyl- 5 inders-and substitution ofmanifolds, etc., to produce the proper and necessary passages. maticvalves responsive to air pressure have been provided in the substitutecylinder heads, all as shown in the Schramm patent referred to above.

50 One of the .requirements, in addition to the transformationsindicated above, is the provision of suitable unloading mechanism whichwill stop the compressor action when the pressure in the receiving tankattains a predetermined maximum. This is generally a valve arrangementwhich 7 Autoaccomplished by holding open the intake valves of thecompressor cylinders by means such as illustrated in my prior Patent No.2,023,418, dated-December 10, 1935, so that as the compressor pistoncontinues to reciprocate air is alternately drawn into and 5 forcedoutwardly through the permanently held valve. Unloading of this natureis quite simply accomplished where the valves are of automatic type.

Automatic intake valves, however, are not par- 10 ticularlysatisfactory, inasmuch as, since they depend for their operation uponair pressure, their operation varies quite considerably, depending uponthe pressure in the receiver. Consider, for example, the differentconditions which 15 exist when the receiver contains air at a lowpressure and when it contains air at high pressure. There is alwaysresidual clearance in the 'cylinder when the piston is at its inner deadcenter. The pressure above the piston at this time depends upon thepressure of the receiver and is substantially equal to it. As the pistonthen recedes from its inner dead center position, an automatic intakevalve will not open until expansion of the gas in the cylinder hastakenplace to such extent that the pressure is below atmospheric by an amountsuch that the difference in pressure will serve to open the intake valveagainst the relatively weak spring which acts upon it to normally holdit closed. It is obvious that the distance the piston must move beforesuch opening takes place is very much affected by the pressure in theupper end of. the cylinder when the piston is in its dead centerposition, which pressure is substantially equalto that of the receiver.The action of the intake valve accordingly varies very considerably withthe receiver pressure and design can only be made to effect properworking under oneparticular condition. Desirably the intake valve shouldbe open throughout substantially the entire intake stroke of the piston.

.The use of a mechanically operated intake valve will, of course,insu-re thatthe intake valve will operate the same for Diificulties inunloading then arise. Proposalshave been made to produce unloading bythrottling the intake of air. This procedure, however, is objectionablebecause the vacuum drawn above the piston causes oil to pass into theupper portion of the cylinder where, as successive compression andexpansion of the residual gas takes place, vaporization of the oil andconsequent explosions may occur. There is also the grave danger ofhaving so much oil accumulate that,

all pressure conditions. 45

' automatic safety valves.

because of the close clearances involved, the piston may eventuallybreak the cylinder head.

It is the broad object of the present invention to provide a compressorcombining the advantages of mechanically operated intake valves andautomatic exhaust valves which, it may be remarked,have the greatadvantage of acting as In utilizing this combination, the automaticexhaust'valves can be considerably enlarged so as to take up most, ifnot all, of the end of the cylinders. The efiiciency is therebyincreased, since a very small movement of the exhaust valve is necessaryto provide a sufficiently large passage for the free flow of thecompressed air to the receiver.

It is a further object of the invention to provide improved unloadingarrangements suitable for use in connection with mechanically operatedintake valves. In the preferred form this arrangement involvespermanently holding the mechanical intake valve open without affectingthe continued operation of its operating means. The unloading mechanismis such that as soon as the unloading devices are rendered inoperativethe intake valve immediately commences to operate in properly timedfashion.

The general objects mentioned above, together with subsidiary objectsrelating particularly to details of construction, will be apparent fromthe following description read in conjunction with the accompanyingdrawings, in which:

Fig. 1 is an enlarged transverse section of a compressor of L-head typeembodying the features of the invention and illustrating the improvedmethod of unloading by holding open the intake valve;

Fig. 2 is a diagram showing the associations of various parts with thecompressor of Fig. 1, a conventional unloader valve being shown thereinin enlarged longitudinal section;

Fig. v3 is a transverse section similar to Fig. 1 but showing analternative method of unloading; and I Fig. 4 is another transversesection of the same general nature as Fig. lshowing the adaptation ofthe invention to a valve-in-head type of compressor.

Referring first to Fig. 2, there is indicated therein a four-cylinderengine, the two end cylinders of which have beenconverted intocompressor cylinders by arrangement of parts as shown in Fig. 1,intermediate cylinders being adapted to act as engine cylinders tofurnish the drive. It will be obvious that the invention is alsoapplicable to cases in which there is an individual compressor driven bya motor or separate engine. The substituted cylinder head 4 in the caseillustrated may, as usual, he so arranged as to maintain conventionalconditions at the ends of the engine cylinders; at the same time,

however, providing close clearances in the compressor cylinders tosecure maximum pressures and efiiciency of operation. In the presentcase a substitute intake manifold 6 is illustrated, communicating onlywith the intake passages of the engine cylinders, the manifold beingconnected to a conventional carburetor 8. The intake passages lll of thecompressor cylinders may be opened directly to the atmosphere or, ifdesired, may be connected to suitable air filters to avoid accumulationof dirt in the compressor mechanism. The exhaust manifold [2 may stillbe used. The exhaust valves of the compressor cylinders are renderedinoperative by removing, for example, the intermediate follower elementslocated between them and their operating cams. Preferably, however,particularly where there is a complete transformation to a compressor, asubstitute cylinder block is provided to eliminate the exhaust passagesentirely.

Reference may now be made more specifically to Fig. 1, which showsdetails of one of the compressor cylinders. The exhaust valve which isrendered inoperative is not indicated, but would lie in line with theintake valve above the cam shaft 38. As indicated at I 6, the cylinderI4 is provided with little clearance, the piston l8 being adapted tomove quite close to the lower face l6 of the head to secure goodvolumetric efficiency. A passage 20 serves to provide for the inflow ofair from the intake pasage 10 past the valve 22. The exhaust takes placethrough a conventional valve arrangement located in the head andcomprising a ring-shaped valve member 24 held downwardly by lightsprings to normally close ports 26. Theoutlet passages from -this valvemechanism communicate with a manifold connected, as indicated at 28,with a supply tank 30.

The stem 32 of valve 22 is held downwardly in I of the valve stem 32 anda cam, a push rod which serves for the actuation of the valve once inevery two cycles if the engine is of the fourcycle type. To accomplishthis result, the cam shaft 38 is conventionally driven at half therotary speed of the crank shaft and would normally carry single-lobedcams properly angularly placed to attain desired timing, A cam shaftdriven at one-half the speed of the crank shaft may be used after theconversion, but must then be provided with double-lobed cams 36 in orderthat the intake valve 22 may be opened through every out stroke of thepiston Hi.

In accordance with the present invention, the valve stem 32 is engagedby the head 40 of a screw which is locked by a lock nut 42 in a piston44. The piston 44 is arranged for vertical movement in a cylinder 46 andmay, in turn, be abutted by a cam follower, indicated at 48, suitablyguided in a lower extension of the cylinder 46. The space 50 below thepiston 44 is incommunication with the tank 30 through a line 52 in whichis interposed a suitable snap valve of conventional type, illustrated indetail in Fig. 2.

The snap valve is of the type illustrated in my prior Patent No.2,023,418, dated December 10, 1935. This valve comprises a casing 62surmounted by a bonnet 64 connected to the tank 30. A disk 68, havingplane faces, is located within an upper cylindrical portion of the boreof casing 62 and is adapted for vertical movement between an annularplane seat 66 formed on bonnet 64 and an annular plane seat I4 formed onthe upper end of a bushing 12. The disk and seats are finely ground toinsure airtight contact between the disk faces and the respective seats.The disk fits the bore of the casing loosely, whereby a slight clearanceIII is provided between its edge and the wall of the bore for leakage ofair. A spring 16 extending through bushing 12 normally forces the diskagainst seat 66, its tension being adjustable by inward or outwardmovement of its abutment provided on a screw I8 threaded into theinterior of the casing. A hole extending axially through the screwfurnishes communication between the interior of the casing below thedisk area acted valve and causing faulty seating of the disk.

A fitting 62 communicates with the interior of the casing outside of andbelow seat 54. The

fitting is connected to the air line 52 which communicates with thevarious cylinders 46. Within this fitting is a ball check valve 64resting on a. seat 66 and retained in the fitting by cross pin 88.

In the operation of the device, so long as the pressure in the supplytank is below the predetermined maximum, the disk 66 will be heldagainst its upper seat and consequently the cylinder 46 will be open tothe atmosphere through the ball check 84, which has a faulty fit uponits seat 86 so as to permit a slow leakage of air. Under such conditionsthe spring 34 presses the follower 48 in continuouscontact with theoperating cam 36 and, as a consequence, the inlet valve is opened by thecam during the intake strokes and closed during the exhaust strokes, sothat compressed air is in the tank reaches a. predetermined amount, thedisk 66 is snapped to its lower seat on which it is held by reason ofthe effective increase of upon by the air at'tank pressure.

Air at the pressure of the tank then flows past the check valve 84 andraises the piston 44, opening and holding open the intake valve 22 sothat, as the compressor continues to operate, air is drawn inwardly andforced outwardly idly past By this arrangement the inwith the resultthat the intake valve. take valve is held wide 'open there is littleresistance to flow of the air and consequently no substantial waste ofenergy due to the continued operation of the compressor pistons.

When the pressure in the tank falls to a predetermined nfinimum, the.disk 66 will be snapped against its upper seat by the spring I6 andheld there by reason of the fact that the area on the upper side of thedisk is now substantially reduced. When this occurs, the cylinder 46 isopened to the atmosphere and the compressed air may flow therefrompreferably slowly past the ill fitting check 84. This check is desirableinasmuch as the piston 44 will move downwardly slowly with the resultthat for an appreciable number shaft the valve 22 will not be completelyclosed.

of revolutions of the engine In general, an engine compressor unit ofthis character is furnished with a governor which is somewhat sluggishin operation and permitted to open the engine throttle before full loadis imposed on the compressor. The delay provided by the slow closing ofthe valve 22 during compression strokes of the compressor pistonsenables the governor to furnish su'fiicient mixture to the engine as theload is gradually increased to avoid any sudden shock. Of course, if theshock is immaterial, the check 64 may be eliminated, whereupon, assoonas the valve 66' operates, the inlet valve 22 will be again under thecontrol of the cam 36.

passage 96 from the automatic discharge valve 24 normally communicatesthrough 98 with the receiver. A valve 82 is arranged to alternatively,

seat on an upper seat carried by the lower end forced through the valve24 into the tank 30. When the pressure openedat the'proper times by arocker arm should be ed, it will 36 on the cam shaft. Theof a fitting 94or upon a lower seat 91, in which latter position it will cut of!communication between 96 and 08. A passage. I00 furnishes communicationbetween the atmosphere and the upper side of the valve 92. The valve 92is normally urged in its upper seated position by a spring I02 andcarries, at the upper end of its spindle,

a piston I04 sliding in a cylinder I06 and ar-- ranged to be forceddownwardly by air entering a tube I06 corresponding in its connectionswith the tube 52; in other words, arranged to receive air at receiverpressure. The piston I04 is'sufiiciently large that upon communicationof the upper end of the cylinder the valve 92 will be snapped downwardlyagainst its lower seat 91 with the result that communisame time there isno danger that oil will get above the piston.

In Fig. 4 there is shown substantially the same operative arrangement asin Fig. 1, applied to a valve-in-head type of compressor. In this casethe cylinder is indicated at 0 and the piston at H2. In the cylinderhead there is fitted a member II4 which provides a seat for the valve H6normally urged upwardly by a spring I20 and I22 acted upon by a push rodI24 connected to a piston I26 reciprocating in cylinder I28. The pistonI26 is acted upon by a plunger I30 which forms a follower for the-camI32 carried by the cam shaft I34. The tube I36 corresponds to the tube52 and communicates with an unloading arrangement such as indicated indetailin Fig. 2. It will be obvious that the unloading takes place insubstantially the same fashion as in Fig. 1, the unloading resulting inthe maintenance of valve H6 in open position so that air is idly drawninto and forced out through the passage H8. In this arrangement thedelivery or discharge valve I40 in the form of a ring may be arrangedannularly to the valve II6, there-being provided an annular series ofholes I38 communica'ting with the cylinder. The compressed air is forcedoutwardly through one or more passages I42 to the receiver.

In all of the unloading arrangements illustratbe obvious that during anunloaded period the pressure in the .cylinder remains constantlyapproximately atmospheric, the deviations being only the minor ones dueto friction in the passages and, in the case of the modification of Fig.3, thelight pressure of the exhaust valve springs.

It will be clear that numerous changes in the embodiment ofthe inventionmay be made without departing from its scope.

What I claim and desire to protect by Letters Patent is:

1. In combination, a receiver for compressed gas, a compressor connectedto said receiver to ,deliver gas thereto including a cylinder andreciprocating piston therein, an intake valve for the cylinder, meansfor mechanically actuating.

the intake valve, and an exhaust valve operated automatically by the gascompressed in the cyl- I06 with the receiver valve 24 to the athaving afixed axis driven in timed relationship with the piston to open saidvalve, and means for holding said valve open upon attainment of predetermined pressures of compressed gas delivered by the compressorirrespective of the operation of said cam.

3. A compressor including a cylinder, a piston therein, a valvecontrolling an intake port, a spring urging said valve to closedposition, a cam having a fixed axis driven in timed relationship withthe piston to open said valve, and pneumatically actuated means forholding said valve open upon attainment of predetermined pressures ofcompressed gas delivered by the compressor irrespective of the operationof said cam.

4. A compressor including a cylinder, 2. piston therein, a valvecontrolling an intake port, a spring urging said valve to closedposition, a cam driven in timed relationship with the piston to opensaid valve, intermediate devices between the cam and valve through whichthe cam operates said valve, the intermediate devices including apiston, and means for moving the piston to hold the valve open uponattainment of predetermined pressures of compressed gas delivered by thecompressor irrespective of the operation of said cam.

' ALFRED N. GUSTAFSON.

